Document FR 2 805 656 describes a high or very high voltage DC electric cable.
The high or very high voltage DC (HVDC) electric power cable comprises a central conductor element, and in succession and coaxially about the central conductor: an inner semiconductive shield; an extruded electrically insulating layer; an outer semiconductive shield; a protective metal shield; and an outer protective sheath.
The electrically insulating extruded layer is made from a mixture comprising polyethylene and a styrene copolymer, the content of styrene in said mixture lying in the range 11% to 18% by weight.
Nevertheless, when extruding said mixture around the conductor example, the electrically insulating layer formed in that way presents thickness that is not uniform, and therefore a surface appearance that is perceptibly not cylindrical.
Consequently, the dielectric properties of the electrically insulating layer are affected and are not identical over the entire thickness of said layer.
The invention seeks to solve the problems of the prior art by proposing an electric cable including an electrically insulating layer based on polyethylene and a styrene copolymer, and having dielectric properties that are uniform and good throughout its thickness.